Yellow fever (YF) virus, a flavivirus that infects the liver, causes a self-limited febrile syndrome in 85% of patients. In the other 15%, however, it causes jaundice, bleeding, and renal damage, and half of these patients die. No antiviral therapy exists. In urban settings, YF virus is transmitted between humans by Aedes aegypti mosquitoes, as are Zika, dengue, and other viruses. Outside urban settings, in the jungle or forest (“sylvatic cycle”), YF transmission occurs between monkeys and from monkeys to humans via non-Aedes mosquitoes (1).

The United States had YF epidemics in the 18th and 19th centuries. In the 20th century, epidemics occurred in sub-Saharan Africa, Latin America, and the Caribbean. The first cases in Asia were reported in 2016, when 11 workers returned home to China after having been infected in Angola (1).